You forced the index URL to be https://test.pypi.org/simple/ so pip looks for tensorflow at https://test.pypi.org/project/tensorflow/ and there're only 2 versions that have downloadable wheels suitable for your platform.
If you want to install kmeanstf from test.pypi.org and tensorflow from pypi.org you need to provide an extra URL:
pip install -i https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple/ kmeanstf==0.7.0a4
